1. Field of the Invention
The present invention relates to an Internet access gateway (hereinafter, referred to as IAG) connected to the Internet, and more particularly to an IAG for sharing a single public Internet protocol (hereinafter, referred to as IP) address without a network address translation (hereinafter, referred to as NAT).
2. Description of the Related Art
A local network consists of computers (or personal computers; hereinafter, referred to as PCs) connected with one another by a wireless LAN (Local Area Network). The local network is connected through the IAG with the Internet. For example, the IAG includes customer premise equipment (hereinafter, referred to as CPE), carrier leased equipment (hereinafter, referred to as CLE), etc.
IP addresses must be assigned to information terminals such as the PCs which are connected to a local network of an office, a SOHO (Small Office/Home Office), a home, etc., so that the information terminals may access the Internet. In order to allow the plurality of PCs to access the Internet, the plurality of IP addresses should be assigned to the plurality of PCs. However, it is difficult to assign all the PCs individual IP addresses because the number of IP addresses are insufficient. For solving this problem, NAT and/or PAT (Port Address Translation) have/has been used for allowing the plurality of PCs to share one IP address.
That is, the PC connected to a local network uses a private IP address, and the private IP address is changed to any public IP address assigned to it in CPE or CLE in which the local network is connected to the Internet. Also, port number fields of IP packet fields are differently assigned according to PCs, thereby distinguishing paths of IP packets.
Though a head field of an IP packet, that is, an IP address or a port number, is translated, the IP address in a data field remains as a private address. Therefore, if a system is programmed to confirm that an applied program of a receiving server is not a port number but a data field and thus to respond to it, the system may cause a malfunction or the packet may be transmitted to the Internet in a wrong way. That is, because the receiving server, which receives a packet, reads out not a public IP address from the SRC IP (source Internet protocol) field of the packet but a private IP address from the data field, the receiving server does not correctly determine what is the transmission part and responds as per the wrong part.
Using private IP addresses and changing the private IP addresses to public IP addresses using NAT/PAT, causes a problem since the position at which the IP address is placed is not unified as in a case that an IP information is copied into the data field of a packet.